I echo @MediumRoastSteam and others on this. Use the Lelit OEM screen. Remove it and clean it once a week, ideally in cafeza but atleast weekly well flushed wiped and cleaned with water. I would not go more than 2 weeks without a cafeza clean. Leaving a build up has a noticeable negative impact on taste.
The build up is also a sign that your entirely machine needs a cafeza flush. I cazeza flush my machine (which is not a LE, but the principle is the same) once a week to once every 2 weeks, depending upon extent of use). Again, you will notice an improvement in taste after cleaning.
I would further recommend that you backflush with water before every espresso making session or atleast once a day. I also use a puck screen, which keeps my machine cleaner and reduces puck channelling and can be used to adjust headspace.
