Thank you all for your answers.
If you are posting on this forum for advice, there is no chance at all that you can do this safely.
Regarding safety suggestions: I have already done this several times and am always cautious with 220VAC, I take into consideration component power ratings and not touch any wires when the circuit is plugged into mains, but thank you for your concern.
The conclusion: A 220v/6v transformer with linear regulator is a good and easy solution to get 5VDC in general, but it takes alot of space due to the huge amount of windings due to the big transformation coefficient. To save space, modern converters use transformers with smaller transformation coefficient (220v/22v f.e.), but with such a high voltage difference linear regulators can be thrown into the trashbin and a switching power supply must be made, and that is where the task gets nearly impossible for a hobbyist.
The best option for me seems to be scavenging the guts of phone chargers and fixing them on my general circuit.
For small transformers, search for “control transformer”. Perhaps line these on Ebay..
This could also be a solution, but an expensive one.
Learn about FETs (field effect transistors) as they’re more efficient either full ON or full OFF. Logic level FETs can be switched with 5V, if you buy in tens you can get them pretty cheap. Save relays for switching AC power.
Use a mosfet to conduct AC current to home appliances, is that what you mean? If so, that means 2 mosfets (for each polarity of AC). Would be a good replacement for a relay in terms of efficiency, but efficiency isn’t on the priority list here, since its just like 0.5W of power dissipation through the relays coil.