Well, it comes down to the question of whether or notYes, like @zardoz says, once you renounce your PR you are effectively entering Canada as if it were your first time again, but it might be your only way.
Unfortunately it's the consequence of not maintaining your PR through your residency, or becoming a citizen of Canada (and yes, I'm well acquainted with German rules on dual citizenship).
Interesting, and very helpful once again. I wish I had known about this website earlier... the information I manged to get here in less than 8 hours, is far more useful than anything I was able to obtain in 8 weeks from IRCC directly.Once you renounce your PR status, all your previous time spent in Canada or as a PR will be completely irrelevant to any new application. You will be applying for PR from scratch, same as any other foreign national.
You have no H&C reasons to keep your Canadian PR status, so your only possible way to keep your PR status is to enter via a USA land border, hope you aren't reported for Residency Obligation violation, and then stay inside Canada for 2 straight years without leaving for any reason. If you can't commit to do this, then there is practically no chance for you to keep your current PR status.
Renouncing your PR status is the only way you'll be able to get an eTA approved and fly to Canada directly. As mentioned once you renounce, you'll need to re-apply from scratch under an economic immigration stream if you ever want to re-apply. None of your PR/citizen family in Canada can sponsor you. If you don't qualify under an economic immigration stream (based on your education, work experience, age, etc etc), then realistically you will never be able to live in Canada as a PR again.
A couple of questions regarding your points on keeping my PR status...
If I enter Canada via a USA land border as a short term visitor (i.e. 2-3 weeks to visit family), how could I be reported for Residency Obligation violation if I'm visiting as a foreign visitor, on a foreign passport? If I have a return flight going back from the US, I don't see how that could be considered a violation. My understanding is that the eTA is only required for public travel (i.e. airlines and busses). Prior to the eTA enforcement, I never had issues travelling to Canada as a visitor via my German passport.
You mentioned that keeping my PR status would require me to stay inside Canada for a straight 2 years without leaving for any reason. Does this also include short term leaves out of the country? The reason I'm asking is because according to the online information, a person retains their PR status, if they have been physically present in Canada for a minimum of 730 days within the five (5) years. It doesn't state anywhere that those 730 days must be consecutive. Also, what would this mean in terms of working in the country over the 2-year period? Would I be legally entitled to work during those 2 years (I still have a valid SIN number), or would I need to re-apply for PR status first? If my intention is to return to Canada, I could obtain a work VISA or sponsorship from my current employer, who is also based in Canada. Obviously I would prefer not to do that if it's not necessary.
As for qualifying under one of the economic immigration streams, it's a bit difficult to predict. I have a skilled profession, and worked in Canada for several years in the same/similar field prior to my relocation to the UK. I also have a Canadian post-secondary degree, and immediate family who still lives and works in the country professionally. What I don't have going for me anymore is age. I also have a wife and child, who are both European, which also seems to deduct points. It's really a shame that there are no better options available for someone like myself, who has worked and paid their taxes in Canada for the majority of their adult life.