I have 2 android devices, asus and xiaomi. I don't really use much them, meaning the few times I do I have several standing updates, most of them from f-droid.
On debian I enter a command and the machine downloads and executes all standing upgrades at once.
I don't know if I don't understand android, but on the gui I have to first download the application and then click again to install it. I am never shown an option to bulk download and install, which would save much time.
Is it supposed to be like this? Is there something I don't know?
I am currently using the Droid-ify client for F-Droid, and I can definitely update all my apps at once. I believe this "update all" option exists for the official F-Droid client (as well as other third-party clients), it might just be a colourful icon rather than text that you don't recognise.
I have it configured to install with Shizuku, if the default "session" installer doesn't work, it might be worth a try!