I spent 3 years searching very hard, (I was over 63 y.o.) and observed that www.jobs.ch seemed to have all the advertised the jobs.
However remember to make fresh contact with all your old work mates, and old employers. Many jobs are never advertised! Eventually I found a job via a friend of a friend, it lasted for 2 years with Swisscom IT Services in Bern. I finally retired when I was nearly 66 years old !
Many job hunting sites in CH use the database/resource of jobs.ch. So you may find some duplications. However sites from other countries are pretty useful such as jobserve.com (UK) or icjobs.de (DE)
Instead of LinkedIn, create a Xing profile ( www.xing.de ) and wait for the job to find you Seriously, Xing is much more popular than LinkedIn in German-speaking countries (so called DACH Region). Good Luck!