Now you have the extension built, and you have two options for getting it onto your device:
1. Pay $100/year for a developer license, create your own testflight for yourself and your friends, upload it, there you go
Or
2. Move to a european country to enable side-loading, pay $100/year for a developer license so you can sign it, and then sign + sideload it. (it's not really true sideloading, but if you're in the EU you can at least do it without testflight https://doesioshavesideloadingyet.com/ )
Oh, also, if you don't have a mac of some sort, you'll have to buy one. A mac mini is pretty cheap.
You can also buy an android device and install any extension on firefox-for-android for free without paying apple, or anyone, $100/year.
You don't need to do a full reinstall each week, getting another provisioning cert works.
You can run altstore on a machine on your network, or reprovision on the device itself to re-sign the app mostly automatically. The latter does use one of your account's five free app slots though.