I found the answer: the little drawer icon on the right is the 'mark read' icon. Click that and then you can select what to mark read. Clicking 'all' will mark everything read.

@Lakotaubp thanks for the reply. I was refering to the app. Clicking the hamburger menu with the unread count just lists the categories and doesn't seem to offer an option to mark posts as read.

Is there any way to mark topics as read in the forums app?

@krampq Running any OS on mobiles relies on hardware drivers that were written for android. Those drivers are proprietry code (not open source) so have to be supplied as binary files by the manufacturer and different files are needed for each model of phone and each version of android. Halium is the (h)arfware (a)bstraction (l)ayer and it talks to the manufacturer's device drivers. The linux kernel sits on top of that. Apps (mostly) run in containers, which is what the clicks are, and they are sandboxed from the os, which is mostly mounted on a read only file system. So really it is quite different to many linux systems as far as apps are concerned. Clicks are somewhat similar to snap packages. Hth

Just been given a Nexus 5 with UT preinstalled. I love it so far. Looks very simple to write apps for. I have a pwa i'd like to port to UT, so I'll be setting to work on that. I have Mint on my laptop. Also have access to a Oneplus to test out focal packages.