Another limitation with Lightroom
Played around this a bit more: Lightroom will only send a raw file to Photoshop or Elements. The best it will do for non-adobe products such as Affinity Photo is to convert and send a file with the following choices:
File format: TIFF, PSD, JPEG
Colour space: ProPhoto RGB, AdobeRGB (1998), Display P3, sRGB
Bit depth: 8, 16 - JPEG is limited to 8 bit
With TIFF there is a choice of compression if desired.
So using a Lightroom/ Affinity Photo workflow, you would be doing RAW edits in Lightroom. I don't planned to renew my subscription when it ends in April, so hope Affinity has a DAM product by then.