Years ago I saw a couple of tools in use, one was like a giant glass cutter wheel mounted in front of an aluminium foot plate, a serrated lever engaged on the floor - thus driving the smooth but sharp cutter wheel forward acting as a tongue cutter. The other was similar but had a small dia circular saw blade rotated by a ratchet handle, this was the cross cutter. Both were slow by today's standards
I am trying a 'mini circular saw' as I've never been happy with the results of the full sized ones, as people often want to stain & feature boards later. These little saws have a slimmer cut or 'kerf' - so it is less noticable when reinstated. Mine is an argos version of the 'Batavia speed saw' others include Worx Handy Cut, & Exakt DC270. I went with 26 mm max depth rotary cutting rather than one of the oscillators. I found the forum while looking for better ways to lift boards. The Batavia is dearer (& not all metal built) but would cut closer up to the skirting than mine does.
The Exakt I mention cuts 25 mm deep, rather than the early 12mm depth model, the worx is 22mm