Cover/remove any brand name labels. Duct tape and spray paint are ugly. Use them.
Lock it to something solid. Use multiple, high quality locks if you can. Lock it where there is video surveillance if possible. Never leave it long. Never ever leave it outside overnight.
Greetings from Berlin, where more than 25,000 bikes are stolen each year. That’s 70 per day, or 3 per hour.
Despite following my own advise above as best I could, I have lost 3 bikes in the last 20 years. I still ride a bike everywhere though, 100% of the time, averaging over 5000 km a year.
Get out there and explore your city!
Edited to add, a good lock is going to cost a lot more than a standard one, and will easily weigh over 5kg.
A problem as old as the hills. I solved that problem many years ago by moving away from KDE, lol. Sorry I have no applicable advice.