The classic big hillwalking horseshoe of the Lomond Hills links the three main summits in one long round. If you're based in the area and can't get as far as the highlands, this makes a great keeping-it-local stand-in; but it's a lot more than just a substitute, and well worth the journey from further afield when lockdowns permit.
Alternatively, start and finish in Falkland - either go directly up East Lomond and down Maspie Den, or vice versa, and when restrictions are eased, enjoy coffee and cake at Camerons, in the High Street, or at the Pillars of Hercules, a mile or so out of Falkland on the road to Strathmiglo. Falkland also has a rather fine palace to visit, with the only real tennis court in Scotland (I think).