Izzyondroid (the weird 90s looking store) can be used with the (or any) fdroid client. You just have to add the repository in the settings. Fdroid builds all the apps from source themselves. You need to add a request for packaging and even after that it takes a bit of time until the app is approved. It seems nobody has requested the inclusion yet. Izzy on the other hand takes the developer build binaries and publishes. The requirements are lower to be included here. So apps tend to be in izzy first and then get eventually added to fdroid proper.
Is there a reason why thunder is only on a weird, very 90s looking app store and not F-Droid?
The apk is available on the github page, so you can just download and install from there.
Izzyondroid (the weird 90s looking store) can be used with the (or any) fdroid client. You just have to add the repository in the settings. Fdroid builds all the apps from source themselves. You need to add a request for packaging and even after that it takes a bit of time until the app is approved. It seems nobody has requested the inclusion yet. Izzy on the other hand takes the developer build binaries and publishes. The requirements are lower to be included here. So apps tend to be in izzy first and then get eventually added to fdroid proper.