In my dev laptop I installed an SSL cert using mkcert. Works fine in all desktop browsers. They don't even prompt to accept the "risk" and continue. But in my Android phone on the same LAN (with the dev subdomain in dns) I get that prompt from both Chrome and Firefox. That would be acceptable, except Firefox prompts pretty much every time I return focus to the app. It gets annoying having to click two extra buttons (Advanced then Accept Risk and Continue) for every code change that needs to be tested in all browsers.
Is there any way to make Android Firefox permanently accept the cert or any other solution?