I do not have tlauncher (learning what that is right now). I opened this ticket due to the REALMS-5939 showing for a MAC and I have a PC (in case that matters at all).
I am experiencing similar if not the same issue.
update: My issue appears to be resolved. (no changes that I am aware of were made)
This appears to be resolved for me. I'm not sure if this is related to any changes made on Mojang's end, but I can tell you there have been no changes on my end or the Realm owners end.