I finally did it. I fulfilled my first assignment and sold rare items, even with the still active suspension of "Rare Goods Trading" according to (the first post in)
https://forums.frontier.co.uk/threads/elite-dangerous-powerplay-2-0-update.630423/.
This is how/what I did (it):
First: I searched for a system controlled by Yuri Grom, that is 160ly away. I search with this website:
https://www.edsm.net/de/search/stat...istanceCMDR/type/1/type/2/type/3/type/11/p/10. The nearest system (with at least 160ly distance from Shinrarta, where I bought my rare goods) was Truku. I searched for Truku in the galactic map and found an previously unused switch in the 2nd column, which allowed me to show the acquiring systems with a small white circle each as visible in the image below.
The first system I then jumped to had neither a settlement nor a station, the second only an Odyssey station (I'm still playing Elite Dangerous: Horizons). But the third system "Eithure" had a space station. I then doublechecked if there was at least one system within a 20ly radius, that is controlled by Yuri Grom by using this link:
https://www.edsm.net/de/search/stat...DR/type/1/type/2/type/3/type/5/type/6/type/11. Thankfully there were 2 systems within that range. I landed in Eithure's space station, sold the rare goods and now I am finally in PP2.0 rang 1.