gpff

Probably soon here https://www.scaleway.com/en/pricing/model-as-a-service/

This case is cute and well built but it does have strange quirks, see also the noisy PSU [1]

[1] https://community.frame.work/t/noisy-psu-fan/74751

I made myself such a tool: https://pdf.rere.re

It's js only, nothing is sent to the server. It automatically makes the background of signatures transparent. The result is a raster pdf as if you printed, signed and scanned the document. I use it on desktop, not sure if it works well on phones.

Let’s Encrypt cross-signature with IdenTrust "DST Root X3" is ending on September 1, 2021 but 33.8% of Android devices are running versions under 7.1 which don't trust Let’s Encrypt new root certificate "ISRG Root X1"