Moved into new (to us, built in 1980) house 2 years ago. Installed an Airthings radon meter a year ago. Levels get up to 400 Bq/m3 when all the windows are closed. Finally had a radon mitigation system installed. Will hopefully get to much safer level below 100 Bq/m3.
To be fair, I never heard of someone needing to fix their home build parachute nor switching to boughts one either.
The point is that when your life depends on it, you perhaps shouldn’t DIY it.