Outstanding!! That was my plan in the same year when Boris instigated the very first lockdown! Bought my camper the day before lockdown and it sat on my drive all summer! My plan was to drive to Crete and then spend a few months Island hopping around the Aegean.
Im in the south of England so my personal choice of route would have been crossing the channel via ferry or train into Calais or Dunkirk, then, depending on whether youre in a rush or not, drive across France, crossing into Swiss at Basle, drive across Swiss and exit at Chiasso on the Swiss / Italian border, then on down to Milan. Scoot around the Tangenziale, the Milanese ring road, and on down passed Piacenza, Modena, Bologna, Rimini heading to Ancona. You can get a ferry from Ancona to Patras or Pireaus, your choice, and then on to Rhodes via a separate ferry from Pireaus. If you fancied it you could head further south in Italy and get a ferry from Bari across to Greece which I believe is cheaper and a shorter crossing than using Venice or Ancona but then again you are driving more miles and using more fuel to get there.
If I was coming from Bruges then head down across Belgium, around Brussels and down into Lux then fill up with diesel there, its very cheap, then carry on, out of Lux and down through France. If I was in a rush then I would cross into Swiss at either Basle or Vallorbe and carry on across Swiss as previously stated, if not in a rush then stay in France, enjoy the drive and cross in to Italy via Mont Blanc or Frejus tunnels. If youre feeling adventurous you could go over the top on the old road and cross into Italy via Mont Cenis. Personally I wouldnt go via Germany, the autobahns can be a nightmare for roadworks etc and as stated by Shaun, in Austria you would have to pay the Vignette.
If you went through Swiss and exited at Chiasso, its about a 3.5 to 4 hour drive to Venice from there. Head down to Milan then Brescia, Verona, Vicenza, Venice.
Tips....Give yourself a few trial runs at changing a wheel for the spare , if you havent done it before.
Make sure you have a hi-viz for everyone in the vehicle, two warning triangles, a small fire extinguisher, head torch and hand torch, spare bulbs, spare spectacles if you wear them for driving. Different countries have different requirements so best just to cover your backside and take the lot.
Have an old fashioned PAPER MAP or maps!! Dont just rely on sat-navs and tech.
Take the original V5 and copies of your insurance, you may not legally need them in some countries but you will save yourself a world of pain if you can produce them when asked.
Keep an eye on the 90 / 180 day Schengen rule.
Have you got European roaming set up for your phone?
Confirm with your insurance company what their procedures are for "what happens if.........."!!, IE breakdowns, accidents, recovery, repatriation, emergency accommodation, hospital fees etc and confirm the contact telephone numbers and email addresses.
Make sure you and all other travellers have your UK Global Health Insurance Card.
Sounds like a great road trip, im well envious!!! Enjoy!!