https://www.synthcamp.org/ - Finland yearly synth retreat
https://pif.camp/ - a coool week hacking in the mountains of SOCA vally (solvakia) (also heavy on synth stuff)
https://mechatronicart.ch/tag/homemade/ - homemade camp by the swiss gang
https://www.circuit-control.de/?lang=en - circuit control in drezden in the week of DIY synth making