Fontconfig error: Cannot load default config file

[nuke-web3]

On build and run, I get:

Fontconfig warning: line 5: unknown element "its:rules"
Fontconfig warning: line 6: unknown element "its:translateRule"
Fontconfig error: line 6: invalid attribute 'translate'
Fontconfig error: line 6: invalid attribute 'selector'
########### snip #####################
Fontconfig error: "/etc/fonts/conf.d/90-synthetic.conf", line 6: invalid attribute 'xmlns:its'
Fontconfig error: "/etc/fonts/conf.d/90-synthetic.conf", line 6: invalid attribute 'version'
Fontconfig error: Cannot load default config file

Desktop (please complete any relevant information, or leave this section out if not applicable):

• OS Ubuntu MATE 20.04
• Fuzzr version (https://github.com/FuzzrNet/Fuzzr/commit/60c130b0b006c1a404b8c27f60cbc29f84000540)