It's not Signal's fault that Apple does not let you access the most basic feature of an operating system - the filesystem.
I believe in the UK you are legally barred from having access to iCloud ADP.
Apple are still busy fighting the UK government on it in closed-court.
Apple-bashers can continue their hate, but give Apple their due:
1. they are going in all guns blazing fighting the UK government instead of rolling over
2. if they succeed, I think they well-deserve the credit.