I have been using Langis (patched version of the official). There is an older post here Langis (Signal name inverted) for android without Gapps or microG installed. Langis is Signal spelled backwards. I have been using Langis for many years. I also send up debug logs like in the official version with new updates if i see red (errors). So signal knows there are folks using forks such as Langis, Molly, Twinhelix, etc. I believe they don’t like apps that actually use their trademark name and not stay true to the license terms.