Last week I installed new RB2011L-RM and Omnitik. Both connected to SMC switches. Both not working with them.
SMC switches were old model SMCGS24C-Smart and new SMCGS18C, both with latest firmwares.
I have another RB2011L(-IN) for testing on the table, problem is the same.
Link status LED indicate link up, everything look as usually, but no communication between them. I tried lot of patch cabels, crossed cables, tested connection to 1 Gbit part of mtik, 100 Mbit part, tried administratively slow down port from Gbit to 100 Mbit. I tried ROS 5.22, 6rc5, 5.17. I tried using HW switch chip in Mtik, without using switch chip (interfaces only in SW bridge). None of this work as I expect.
Mikrotiks and switches individually work (switchs) without problems. When I connect Mikrotik to nonmanagement old 100 Mbit SMC switch, all works normally.
I plan test RB2011 against SMC Tiger switch and D-Link smart switch.

Do anybody has experience with this problem (new Mikrotiks model vs SMC switches)?

I apologize for my bad english.

I've got a simililar problem with the RB2011 and a Zyxel IES-5005 DSLAM.

I cannot connect the RB2011 to the DSLAM with fibre-optics.
It won't even show a running interface.
It didn't matter which RouterOS or which kind of SFP I used. (650nm, 1310nm, 1000M, 100M)
The only solution to get a working link is to use Copper-SFPs (SFP to RJ-45). But fibre-links NEVER worked.

in RouterOS you can try to use
/interface ethernet monitor <interface-name> to see actual statuses of the interface, what it reports etc. maybe there is some weird VLAN configured on these switches or some other weird stuff happening. As devices are tested with various devices before and during manufacturing.

Interface status says normally link up, on 1Gbit (or 100Mbit). Everything looks as usually. Mikrotiks and switches are factory defaults, no VLANs or another configurations.
I register this problem on 3 factory new mikrotiks (2011L-IN, 2011L-RM, Omnitik), and tested with factory new SMCGS18C and old SMCGS24C-Smart after factory reset.
With old model of Mikrotik (RB750, ROS 5.16, 5.22) switches communicate without problems.

maybe you could point us to place where we could get one of those switches to check out what is going on?

Link-ok usually means that negotiation was successful and it should just work.

Deleted because not related.

Thank you Dobby.
Today I tested RB2011L (5.22) with SMCGS24C-Smart and found the problem.
The problem is firmware of SMC switch. When I use latest 2 firmwares (v2.5.0.1 and v2.5.1.5 downloaded from SMC site), Mikrotik not able to communicate with switch. When I use factory firmware (v2.2), all work without problem.

Unfortunatly, I haven't SMCGS18C-Smart for testing now. This new models have factory firmware and I can't find any version of (newer) firmware to download.
I guess, this problem is on all new models of Smart SMC (SMCGS10,18,26,50).

I think, it is problem of SMC, I tested Smart switches from other vendors and they worked without problem (see list below).

SMC-EZ1016DT OK (no management)
SMCGS24C-Smart FW: 2.2 OK
SMCGS24C-Smart FW: 2.5.1.5 KO
SMCGS24C-Smart FW: 2.5.0.1 KO
SMCGS18C-Smart FW:from factory KO
TP-Link TL-SG3109 OK
D-Link DGS-1100-16 OK

Deleted because not related.

probably L1 derrivation from standard.
saw such struggle between 3Com and Intel switches in past. and HP rejecting D-Link
check switch phy/trx datasheet in SMC and send report/request to vendor.