Here are some precomputed stats, which are reasonably up to date as I'm writing this (9 Sep):
According to the data compiled by Farm Europe on this topic, a total of 96 outbound vessels exported grain under the UN deal as per the operational updates from the Joint Coordination Center received until 6 September, which also included the boats that were to depart on Wednesday 7 September 2022 (the day of Putin’s statement).
These figures indicate that EU member countries received 795,017 metric tonnes out of the total 2,171,936 metric tonnes of cereals exported from Ukrainian ports. That means that around 1,376,919 metric tonnes of grain and foodstuffs went to non-EU countries. Even so, by subtracting Turkey’s figures of perceived grain out of this amount, a total of around 937,429 metric tonnes of exports remained available to third countries. [...]
the amount of grain that was sent to least developed countries, according to the UNCTAD classification of least developed countries, was of a total of 125,840 metric tonnes of grain: Sudan received 65,340 metric tonnes of grain while Ethiopia and Yemen (reported under the unclear category because they passed through other intermediary destinations) received a total of 60,500 metric tonnes from the vessels Brave Commander and Karteria under the UN WFP.
As I mentioned in a comment, the raw data is available for those who want to do stats. One thing that's apparent by a quick inspection is Turkey was the destination of many small[er] vessels.
Also, some of the Asian countries that were the destination aren't necessarily poor either. But yeah, least developed countries only got like 5% by tonnage in that analysis. (Mind you, even India or Egypt don't count as being in that LDC category.)
That source doesn't do the sum for developing countries, but using this wiki map some EU countries actually still count as developing, so the list of developing countries among those is: Turkey, Iran, Romania, Egypt, Libya, Sudan, India, China, Bulgaria, Kenya. I get a total of 1.14 million tons for those (so about half of the exports by tonnage), albeit Turkey took 38% of that. Egypt comes 2nd, China 3rd and India 4th in that developing countries cat (although Romania isn't far behind) and then Sudan, Iran, Kenya.
Excluding Turkey (as having a customs union with the EU) and Romania+Bulgaria, the non-EU developing countries got some 618,321 tons, i.e. about half of the exports to developing countries, or little more than a quarter of the total.
A few days later (Sep 12), the UN JCC that organizes this has put out its own destination stats, which (caveat) include considerably more total tonnage:
As of noon on 12 September, 2.7 million metric tons of grain and other foodstuffs were moved from the three Ukrainian ports. [...]
Destinations: 28% to low and lower-middle income countries: Egypt (10%), Iran and India (5%), Sudan and Kenya (2%), and Djibouti, Lebanon, Somalia, and Yemen (1%); 27% to upper-middle income countries: Türkiye (19%), China (8%), and Bulgaria (<1%); and 44% to high-income countries: Spain (13%), The Netherlands (8%), Italy (7%), Republic of Korea (5%), Romania (4%), Germany (2%), and France, Greece, Ireland and Israel (1%). Destinations indicated are based on information received at the JCC and may change based on commercial activity. Grains that reach a destination may go through processing and be transshipped to other countries.
[footnote]: As per World Bank’s classification of countries by income