The only dex-based ranged weapons you can use sword and board are a dart, dagger or net. That is all your options right there without taking an entire action to doff your shield.
Strength-based sword and board is way better when it comes to ranged attacks.
That's arguable. Those weapons have shorter ranges. Though the net is an interesting case because it is cheap and also requires the target to use their action to escape -meaning that they're not gaining an action on you in the event you need to use one of yours to re-equip the shield.
Dropping an item is a free action. Attach a lanyard to the shield so you can drop it for free when necessary and still have it attached to you.
(Honestly, that's a little weird to me, but 5e shields are very ambiguous concerning what type of shield they are. Bucklers? Shields with arm straps? Light? Heavy? With some shields, a shield sling makes sense. )
If you're at the range where longbows and such are useful, one action to re-equip isn't bad. Before that's even necessary, it may be that you have several turns of damage output without the enemy being able to retaliate at all.
Range 150/600 (longbow) vs 30/120 (javelin)
If I'm at a range of 30ft, I'm already effectively within melee range for a lot of encounters (as a lot of things have a movement speed of 30). I suppose there may be scenarios in which the target cannot get to you with movement, but, in that case, they're not able to engage me in melee anyway so I would stick with the ranged weapon.
Though, I would agree that the javelin is likely the best option for throwing.
I think it's somewhat strange that equipping a shield takes an entire action but equipping a weapon doesn't, but those are the rules.
