When using the “Microsoft Flight Simulator” and “Light” themes, the category banners on top of all category and subcategory pages in Sim Update 16 Beta | MSFS 2020 are black on black, making most of the text illegible.
In the “Dark Blue Theme” theme, the background is pink or salmon, so the text is legible.
Category tags (e.g. Sim Update 16 Beta | MSFS 2020 > Regressions ) appear to have their own CSS in the banners, as they are also black on black, but the background is slightly lighter.
I haven’t tested this extensively on mobile, but at least the “Microsoft Flight Simulator” theme is showing black on black there, as well.
Edit:
They’re also black on 
Sim Update 2 Beta | MSFS 2024 category and subcategory pages, as well. This must have just recently happened.