I feel like focusing on the feeling of my feet on the ground is easier than focusing on the sensations of the breath. Is this a viable object for access concentration/jhana?
Jhana is not "access" concentration. Jhana is called "attainment" concentration.
Focusing on the feeling of feet on the ground may result in access concentration (because the mind may be relatively open, pliant & non-attached when focusing on the feeling of the feet) however:
The focus should not be overly forced or rigid because, for access concentration to occur, the mind must have the pliancy to fall into the body.
When access concentration occurs, the mind will automatically experience the breathing.
Methods such as feeling the feet on the ground; listening to silence via the ears; or sitting with a very quiet non-doing non-ambitious mind are often more effective in manifesting access concentration (than clumsy direct attempts at watching breathing). Because the Buddha actually taught his Path is the abandonment of craving, often practise is counter-intuitive.
the way to set the citta into samadhi has nothing to do with concentrating on an object. at best concentration is ''alertness''.
The way to set the citta into samadhi is first to be good at sila, meaning to be good at ''mindfulness'', then to use right view to transform this ''alertness'' into samadhi.
the buddha explains to nanda how to be good at alertness here https://suttacentral.net/an8.9/en/bodhi
then the buddha explains to upali how to set the citta into right samadhi here http://obo.genaud.net/dhamma-vinaya/ati/an/10_tens/an10.099.than.dto.htm
"Having abandoned these five hindrances—imperfections of awareness that weaken discernment—then, quite secluded from sensuality, secluded from unskillful qualities, he enters & remains in the first jhāna: rapture & pleasure born of seclusion, accompanied by directed thought & evaluation.
in details and summarized, https://www.accesstoinsight.org/tipitaka/an/an11/an11.002.than.html
"For a person endowed with virtue, consummate in virtue, there is no need for an act of will, 'May freedom from remorse arise in me.' It is in the nature of things that freedom from remorse arises in a person endowed with virtue, consummate in virtue.
"For a person free from remorse, there is no need for an act of will, 'May joy arise in me.' It is in the nature of things that joy arises in a person free from remorse.
"For a joyful person, there is no need for an act of will, 'May rapture arise in me.' It is in the nature of things that rapture arises in a joyful person.
"For a rapturous person, there is no need for an act of will, 'May my body be serene.' It is in the nature of things that a rapturous person grows serene in body.
"For a person serene in body, there is no need for an act of will, 'May I experience pleasure.' It is in the nature of things that a person serene in body experiences pleasure.
"For a person experiencing pleasure, there is no need for an act of will, 'May my mind grow concentrated.' It is in the nature of things that the mind of a person experiencing pleasure grows concentrated.
Puthujjanas who lack sati will never understand this part
''secluded from sensuality, secluded from unskillful qualities''