[RPG] ny published material regarding the Dragonlance campaign setting in D&D 5th edition

No, this does not exist in 5e.

Implementing it in 5e may be less satisfying, since the increase in proficiency bonus covers many of the incremental advancement options from previous rulesets in one swoop.

So for the fighter, for example, you'd have two options - the one feature they get every level or the proficiency advance they get every 5th level. It's pretty difficult to make that incremental. Even with something like a druid, they get a spell advance and then 0-2 other improvements. Within a single level there's not enough advance, on average, to break it up much.

Another way to implement incremental advancement is to let the character apply the next larger proficiency bonus to one of (attacks, saves, skill checks) per level they go up (not between levels). That seems pretty fiddly, though, and lets someone min-max what they're already good at levels ahead of time.

As you have said you are willing to consider Spelljammer rules, I can pull a few quotes in for you that might help clear this up.

From Spelljammer Core Rules: Book 2, Concordance of Arcane Space, p. 17

Clerics in Space: A cleric may not regain spells above 2nd level while in the phlogiston. This is because he remains out of direct contact with his deity.

A cleric who enters a foreign crystal shell is similarly restricted. The only exceptions to this occur when a cleric's deity (or a similar power) is recognized in the foreign shell or the cleric casts a successful gate spell, affording his deity access to the foreign shell.

Any god or power is considered "recognized" within a sphere if he has worshipers and/or an organized church anywhere within that system. This does not mean that a PC cleric can move into a shell and automatically establish a base of worship for his god. For a deity to be a recognized power in any shell, he has to have an established base of worshipers somewhere in the system.

Additionally, the same rulebook adds the following spells on page 22

Contact Home Power (2nd level Conjuration)

The user of this spell establishes a tenuous link through the Astral Plane between his present location and that of the power he venerates. This link permits the priest to regain his spells as if the god is recognized and venerated within the sphere.

The duration of the spell is one week, as long as the cleric remains in the same crystal sphere in which he cast the spell. Passage into another plane (even the ethereal) will break the spell.

and

Detect Powers (2nd level Divination)

[This spell] allows a cleric to determine if there are friendly gods and/or other powers within a crystal sphere so that he may recharge his higher-level spells within its borders. It also reveals if the god(s) revered by the cleric are worshiped within that sphere.

In this case 'friendly' is defined as 'same basic attributes and portfolio' or possibly 'same god by a different name.' As two examples...

-Paladine and Bahamut are the same god, but known by different names and roles in two different spheres.

-Reorx and Moradin are two distinct gods (from Krynn and FR respectively), but they are sufficiently similar that a cleric of one could receive spells from the other.

So, if you take these pieces of information into account, it gives you the following answer:

When you are on a different world within the Prime Material Plane, you may only regain spells up to 2nd Level unless

1: Your god has an established base of worshipers on that world, or on another world within the same Sphere. This implies that the other gods in the system don't actually get a direct say in the matter...though they could certainly stamp out 'heretical religions' if necessary.

2: You use Detect Powers to locate a friendly deity (or your own) and refresh your spells via them.

3: You use Contact Home Power on a weekly basis to 'phone home' and keep that connection open so you may reload your spells.

4: You use Gate to connect directly to your deity's domain and refresh your spells from them directly.

Now, I do not have access to the Planescape books, so I am not 100% certain that this isn't contradicted somewhere in those books...but if you are willing to abide by Spelljammer rules, that's how it works.