@fp3plusrt
According to this post on the XDA-Developers forum, the "rescue party" - as the screen is seemingly called - should be fixable.
It is mentioned that some keys got messed up somehow, so you should be in need to flash some stock ROM. Dunno which ROM is meant exactly and if this is even of any help but you may try this approach.
Gr33ting5,
3r853n.

@fp3plusrt said:

Want to try Halium 10, which is to be installed from (Fairphone OS) FPOS Android 10.
[...]
Where can I find a stable Android 10 for FP3+ ?

@dr4Ke, here you go:
https://forum.fairphone.com/t/ubuntu-touch-installieren/74814/7
It's a thread in the Fairphone-forum where Luksus posted an FpOS (FairphoneOS) Download.
Still works, since I've just done installing UT on my FP3, even tho it's not the latest FpOS based on Android 10.
Just follow his (Luksus) advices and you will find the way to succeed aswell. But since it's a german Thread I will tell how I did it.
I just booted into a TWRP.img thats been made for the FP3 and cleaned Cache and Data.
Second I restarted into Bootloader where I used the FP3_Flashall (as described here: https://support.fairphone.com/hc/en-us/articles/360048660371) which I got from the ZIP-file that can be downloaded through the second link in Luksus' posting.
Afterwards you could directly run the Ubports-installer Luksus wrote. Nevertheless tho I just tried the ROM and enabled ADB. But I guess that could be skipped just as he wrote.
Best of luck,
3r853n

Hello Folks,

I'm another +1 to the request of @dr4Ke.

@picrard Would you please be that kind, uploading the file once again and sharing the link with us? Since I'm aswell unable to find it on the web?

And @Luksus what would you recommend as a source for the "latest Android 10"? I just don't get how to proceed from my stand. Since I tried my selfcompiled-LineageOS 17.1 as a base for porting my FP3 to Ubuntu Touch but - as you mentioned -, it is not working I must go with the FairphoneOS - which is not available on the vendors servers anymore (neither do they give the instructions or show the way to the source to compile the Android 10 ROM..)!
I am indeed lost with my ambition to try Ubuntu Touch.
Kindly asking you both to assist us here.

Greetings,
3r853n