I've been experiencing delays too but only on the first request. This was due to uBlock Origin initializing. On mobile, this load time adds up really fast as it takes around 5 to 10 seconds for uBlock to load. In the mean time, requests are configured to be delayed. The aggressive Android memory cleaner doesn't help as anytime you close your browser, it reloads again.

All this to say, you might have an add-on delaying network requests to match them against a blacklist, save metadata or whatever the add-on is supposed to be doing.