Thanks for your feedback above which shared more information and glad to know that your issue is resolved now! Since our forum has the policy that The question author cannot accept their own answer. They can only accept answers by others, and according to the scenario introduced here: Answering your own questions on Microsoft Q&A
I would make a brief summary of this post so that other forum members could easily find useful information here:
[Teams Dark Mode - Teams Menu is still in light mode and difficult to read - Summary]
When using Teams in Dark Mode I notice that the list of channels in a Team is still shown in Light Mode and the text colour is so light it is almost unreadable
Try clearing Teams client cache file. Searching for dark mode on your pc and open colour settings. And change all options to Dark Mode. Then try changing Teams to 'Follow operating system' instead of Dark Mode
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