Overleaf supports a fair number of OTF/TTF fonts in different scripts. Their names are listed below, and you can see a sampler here. We also have Google Noto fonts as included in Ubuntu 20.04.1, so even if you don't see the listing for a particular language here, you can try using the relevant Google Noto font for that particular language or script.
(Use with mathspec
or unicode-math
)