Installing LyX 2.3.6.1 on Linux MInt 20.3 with TeXLive 2021

[Graeme]

I've just done a clean install of Linux Mint 20.3, and then a full 
install of TeXLive 2021, which cannot be done with the Mint's Synaptic 
Package Manager. Mint 20.3 includes TeXLive 2019 as part of its 
distribution, but I have not (yet) installed that version.

The standard Plain TeX or LaTeX workflows seem to behave normally, so 
I'd now like to install LyX 2.3.6.1 using the (unsupported) PPA 
available on Launchpad at ppa:lyx-devel/release.

However, when I try to install it using Mint's Package Manager, it lists 
a number of standard TeX packages that it claims are necessary, and will 
not proceed unless I also install them. These include:
tex-common
tex-gyre
texlive-base
texlive binaries
texlive-fonts recommended
texlive-lang-greek
texlive-latex-base
texlive-latex-extra
texlive-latex-recommended
texlive-pictures
texlive-plain-generic
texlive-science
tipa

These are mostly TeXLive 2019 versions for which there are already 
TeXLive 2021 versions installed. I'd prefer not to have both 2019 and 
2021 versions of TeXLive installed at the same time.

This prompts a number of linked questions:

a) Will LyX 2.3.6.1 work OK with a TeXLive 2021 installation?

b) Is there a way to force Mint's Package Manager to recognise the 
existence to TeXLive 2021 packages?

c) Is there a way to install LyX 2.3.6.1 without installing the TeXLive 
2019 dependencies? (I'd prefer not to have to compile LyX 2.3.6.1 from 
source.)

d) If I want to install LyX 2.3.6.1 with Mint's Package Manager, will 
this force me to use TeXLive 2019 instead?

I would welcome advice on how to deal with this problem.

Graeme