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.
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.