Hi... just trying to verify I'm not missing anything obvious.
The Mikrotik Way(tm) is to mount the whole active device (wAP-LTE, ltAP, LHGG, etc) outdoors, and none of the pre-built models have the option of connecting external "dumb" antennas, right?
The only way to have the option of "electronics inside, antenna outside" is to self build something starting with a bare routerboard and modem?

Yes, mostly that's it.

There are a few devices (GrooveA 52, GrooveA 52 ac, metal 52 ac) which are fitted with a proper antenna connector (N-type). And there are some possibilities for full DIY (e.g. L23UGSR-5HaxD2HaxD board as a base).

They do sell this pigtail:
https://mikrotik.com/product/acsmaufl

Which should be a hint towards the DIY path, but if I get it right the U.fl connector(s) are on the actual modem card, so it can be applied to *any* of their LtE products.
Example for the WAP ac LTE6:
viewtopic.php?t=160841

But the Chateau series do have external antenna connectors:
viewtopic.php?t=199791#p1026610
those should be the pre-made "device internal/antenna external" approach you are looking for.

Yeah the LtAP, wAPac, and LtAP mini have some "drill-able" holes to install SMA bulkhead connectors. e.g. the wAPac can mount 4 SMAs on the bottom of the unit. So you can run a "pigtail" cable from the modem module inside to some drilled holes. And, Mikrotik does sell u.FL to SMA pigtails for this purpose. But most newer modem modules use the smaller IPEX4 connectors on the modems, so you may need different pigtails depending on a modem.

fitted with a proper antenna connector (N-type)

@mkx, out of curiosity, do you think N are better (or worse) than SMA for 4G/NR? I guess that allow you use thicker cable, but never looked at the math of these things (i.e. shorter the cable the better)

Thanks for the recommendations!
I didn't even look at the Chateau line because well, "home all in one box" and relatively large box at that.
Kind of funny how it's ready for external antennas straight from factory, while the more rugged stuff is not.
It's not the worst choice cost wise, CPU is more than enough, definitely gets on the shortlist for testing.

Having dug a bit more, I'm tempted to find out how hard it would be to mod the hapAX-lite-LTE.
Pics here viewtopic.php?p=1024613 - looks like the internal antenna is plugged-in, not soldered, at least...

fitted with a proper antenna connector (N-type)

@mkx, out of curiosity, do you think N are better (or worse) than SMA for 4G/NR?

I don't know if N connectors themselves perform any better or worse than others. But as you already wrote, when cables are in the question, thicker is always better and N connectors allow attaching way thicker cables than SMA connectors. That is, if one needs to use longer antenna cable. In case when only antenna atrachnent is required, different connector types performance doesn't make much of change, physical sturdiness is most important (and here generally larger connectors fare better again).
The only big diference between different connector types that I can remember off the top of my head is power rating. Not important when average power, passing connector, is less than a Watt, but it does make a difference when we're talking about tens (or even hundreds) of Watts.

BTW, on the network side of 4G/5G networks, N type is the smaller of connector types used, more often are used connectors type 7/16. Also due to higher power specs.

IDK about the internals of the hAP-ax-lite, but if you're going to DIY there is also the newer L23 board (https://mikrotik.com/product/l23ugsr_5haxd2haxd boards be another option. You can then add a better LTE module than the hAPaxLite. Also, there are external antennas (especially 4x4 ones) that are designed to hold a small router or board like L23 - which minimize the cable length (and associated loss/interference potential).

But if you wanted to go with 5G module... that likely require some M.2 to miniPCIe adapter... Most newer modules are M.2, not miniPCIe that Mikrotik uses on all devices. The wAPacR has USB 3.0 on miniPCIe... while the newer L23 is only USB 2.0 so if you really did have awesome 5G coverage/bandwidth, the USB 2.0 bus speed could be a limiting factor on the L23. And on "big" LtAP, one miniPCIe is USB 2.0 while other is USB 3.0, but it's a MIPSBE CPU & Mikrotik newer features all require ARM-based things (like ZeroTier, which is useful with LTE/NR).

Anyway all the LTE devices have some complex pro/cons. Especially for North America since the hAP-ax-lite have NO overlap with ANY of the common US/Canada/... MNO LTE bands (2/4/12/66/30/71/...).

@mkx, thanks! It's actually the thin pigtails I never like...

thicker is always better and N connectors allow attaching way thicker cables than SMA connectors [... and ...] physical sturdiness is most important (and here generally larger connectors fare better again).

I took a photo of a wAPac with 4 pigtails and an external 4x4 antenna. It works, but it requires the pigtails being exposed with ethernet/SIM/power, so it kinda easy to damage and crossing power.

I took a photo of a wAPac with 4 pigtails and an external 4x4 antenna. It works, but it requires the pigtails being exposed with ethernet/SIM/power, so it kinda easy to damage and crossing power.

Looks neat though. But yes, such things are almost always a problem with DIY projects (or if device designers did not do their job properly).

Thanks for the recommendations!
I didn't even look at the Chateau line because well, "home all in one box" and relatively large box at that.
Kind of funny how it's ready for external antennas straight from factory, while the more rugged stuff is not.
It's not the worst choice cost wise, CPU is more than enough, definitely gets on the shortlist for testing.

Having dug a bit more, I'm tempted to find out how hard it would be to mod the hapAX-lite-LTE.
Pics here viewtopic.php?p=1024613 - looks like the internal antenna is plugged-in, not soldered, at least...

I have modified a hap AX lite LTE to include two external antennae (I used 7dbi omni's) which took the device next level.

I'm just curious though... Why wouldn't you just use a LHGG or SXT outside (as opposed to external antennae)? I think the idea behind them is to minimise cable losses which are more apparent with coax cables over cat5e/6 cables. With an LHGG all the heavy lifting is done within the one unit, hence eliminating coax losses resulting in better signal to noise ratios. There are a few exceptions where a dual array of directional antennae does a better job, but few is the operative word IMO.

I'm just curious though... Why wouldn't you just use a LHGG or SXT outside (as opposed to external antennae)?

The general problem with MT's antennas (and even more with directional ones) is that their gain chart is really shitty. Take a look at LHGG ... indeed antenna gain is specced at 17dBi, but if one looks at low band, it's around 5dBi (for band 20) or even negative (for upper part of band 8 or lower part of band 68). Even for upper frequency bands actual antenna gain is more likely around 15-17dBi (e.g. band 1 or band 3).

There are 3rd party antennas (perhaps ugly looking) with much better radiation patterns and would often much improve overall performance). But then one needs a device with proper antenna connectors (at least FME if not N ... SMA are not physically sturdy enough to attach decently thick antenna cables).