I don't know of any messaging app that will keep the original size by default. I do know however that
whatever default compression used by Telegram is more than adequate to display on a phone or print out
on a printer. If you do want to send the original quality image, you simply send it as a file attachment. The
limit on file attachments in Telegram is 2Gb.
Telegram:
https://telegram.org/blog/profile-videos-people-nearby-and-more
Signal, the limit on file attachments is 100Mb.
Telegram also has some additional editing capabilities and can group multiple photos into albums so the recipient
just gets 1 message with all the photos neatly displayed rather than multiple messages.